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From:   Andy Lutomirski <luto@amacapital.net>
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Subject: Re: [PATCH v38 10/24] mm: Add vm_ops->mprotect()
Date:   Fri, 25 Sep 2020 21:15:19 -0700
Message-Id: <2321E653-F629-44D7-91C3-F42F42AF4EF6@amacapital.net>
References: <230ce6da-7820-976f-f036-a261841d626f@intel.com>
Cc:     Sean Christopherson <sean.j.christopherson@intel.com>,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
        linux-sgx@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>,
        Jethro Beekman <jethro@fortanix.com>,
        Darren Kenny <darren.kenny@oracle.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        asapek@google.com, Borislav Petkov <bp@alien8.de>,
        "Xing, Cedric" <cedric.xing@intel.com>, chenalexchen@google.com,
        Conrad Parker <conradparker@google.com>, cyhanish@google.com,
        "Huang, Haitao" <haitao.huang@intel.com>,
        Josh Triplett <josh@joshtriplett.org>,
        "Huang, Kai" <kai.huang@intel.com>,
        "Svahn, Kai" <kai.svahn@intel.com>, Keith Moyer <kmoy@google.com>,
        Christian Ludloff <ludloff@google.com>,
        Neil Horman <nhorman@redhat.com>,
        Nathaniel McCallum <npmccallum@redhat.com>,
        Patrick Uiterwijk <puiterwijk@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Thomas Gleixner <tglx@linutronix.de>, yaozhangx@google.com
In-Reply-To: <230ce6da-7820-976f-f036-a261841d626f@intel.com>
To:     Dave Hansen <dave.hansen@intel.com>
Precedence: bulk


> On Sep 25, 2020, at 12:53 PM, Dave Hansen <dave.hansen@intel.com> wrote:
>=20
> =EF=BB=BFOn 9/25/20 12:43 PM, Sean Christopherson wrote:
>>> That means that the intent argument (SGX_PROT_*) is currently unused.
>> No, the intent argument is used (eventually) by SGX's ->mprotect()
>> implementation, i.e. sgx_mprotect() enforces that the actual protections a=
re a
>> subset of the declared/intended protections.
>>=20
>> If ->mprotect() is not merged, then it yes, it will be unused.
>=20
> OK, I think I've got it.
>=20
> I think I'm OK with adding ->mprotect().  As long as folks buy into the
> argument that intent needs to be checked at mmap() time, they obviously
> need to be checked at mprotect() too.
>=20
> Jarkko, if you want to try and rewrite the changelog, capturing the
> discussion here and reply, I think I can ack the resulting patch.  I
> don't know if that will satisfy the request from Boris from an ack from
> a "mm person", but we can at least start there. :)

I think I agree. ->mprotect seems reasonable to me.

FWIW, I don=E2=80=99t think I should ack this particular thing =E2=80=94 it w=
as, to a decent extent, my suggestion in the first place, so I=E2=80=99m bia=
sed. I think it turned into something reasonable, and the ->mprotect mechani=
sm seems easily supportable and plausibly useful for other purposes down the=
 road.

>=20
> Please be judicious in what you include in the changelog.  There's been
> a lot of detritus in them.  Let's keep it as short, sweet, simple and on
> topic as we can.